In recent years, atomic layer deposition (ALD) is used as a technique of forming a uniform thin film on a substrate having a large area with a good reproducibility (patent reference 1: Japanese Patent Laid-Open No. 05-186295). The atomic layer deposition is a technique of forming a thin film by depositing atomic layers one after another by alternately supplying materials of respective elements composing a film to be formed. In the atomic layer deposition, one or n layers alone are adsorbed onto the substrate surface while supplying the materials of the respective elements so that no surplus materials contribute to the deposition. This is called the self-limiting deposition. Since the atomic layer deposition uses no plasma, it can form a high-quality film. Still better, since the processing temperature need only be set as low as, e.g., about 300° C. in the atomic layer deposition, an insulating film can be formed even on a glass substrate. Hence, the atomic layer deposition has a feature that it can be applied widely.
An atomic layer growing apparatus to practice the atomic layer deposition having the above-described feature includes a film forming chamber 301 in which the vapor phase growth of a film is performed, a substrate table 302 having a heating mechanism accommodated in the film forming chamber 301, and an exhaust mechanism 304, as shown in FIG. 3. The atomic layer growing apparatus also includes a material supply mechanism 305 including a source gas vaporizer 351 and buffer tank 352, and a purge gas supply unit 307.
In the apparatus shown in FIG. 3, a substrate 303 to be processed is loaded onto the substrate table 302, and the film forming chamber 301 is sealed. After that, while the substrate 303 is heated to a predetermined temperature by the heating mechanism of the substrate table 302, the supply of a predetermined gas by the material supply mechanism 305, the evacuation of the chamber 301 by the exhaust mechanism 304, the purge of the surplus gas by supplying a purge gas by the purge gas supply unit 307, and the evacuation of the chamber 301 by the exhaust mechanism 304 are repeated, thereby forming a desired thin film.
A material (organometallic material) used in the formation of an insulating film by the atomic layer growing apparatus is in the liquid phase at an atmospheric pressure of about 20° C. For this reason, the material supply mechanism 305 vaporizes the material in the liquid phase by the source gas vaporizer 351, and supplies the vaporized material into the film forming chamber 301. Also, the material supply mechanism 305 supplies a source gas into the film forming chamber 301 while a variation in pressure, for example, is suppressed by using the buffer tank 352. At the stage of supplying the source gas into the film forming chamber 301, a supply valve 354 of the film forming chamber 301 is opened while a fill valve 353 of the buffer tank 352 is closed. This control can suppress a variation in pressure caused when the source gas from the source gas vaporizer 351 flows directly.